You are what you eat? Links between a Mediterranean diet and early symptoms linked to Parkinson’s

This study is ‘food for thought’, containing interesting bite size pieces of information that are easy to consume. The researchers have added to a growing body of literature suggesting that a more Mediterranean diet may have a potentially beneficial impact on reducing the risk of developing Parkinson’s. In follow up studies, it would be interesting to see if this diet can also help individuals already diagnosed with Parkinson’s.

The Mediterranean diet is based primarily on the consumption of wholemeal cereals, fruits, vegetables, legumes, potatoes, fish, and olive oil, with relatively low intake of meat and meat products and full fat dairy products. Previous work in the US has shown that individuals who maintained a Mediterranean diet were diagnosed with Parkinson’s at a later age, and a prospective study has also shown that reporting adherence to this diet tended to reduce the risk for Parkinson’s in the future. Given the many open questions concerning the effects of diet on Parkinson’s, these researchers set out to investigate whether people who adhered to such a diet were also less likely to report “prodromal” symptoms for Parkinson’s, that is, symptoms which are often first experienced several years before a formal diagnosis.

Demographic, medical, neurological and psychiatric as well as environmental data were drawn from 1,765 participants in the HELIAD study (HEllenic Longitudinal Investigation of Aging and Diet). This is a population-based study being conducted in Greece, which is designed to assess links between diet and conditions associated with ageing, in people over the age of 65. Although living in Greece is clearly associated with maintaining a Mediterranean diet, the researchers devised a scoring system to capture the degree to which each participant’s diet, according to their own reports, was more or less close to the prototypical Mediterranean diet. Participants were also assessed by a neurologist.

Of the 1765 participants, 34 were found to meet the criteria for a diagnosis of Parkinson’s which is consistent with known prevalence rates of between 1-2%. Using a formula devised by the Movement Disorders Society for the calculation of prodromal or early Parkinson’s, which pools together symptoms of sleep disturbance, constipation, urinary and erectile problems, depression and anxiety, and subtle movement and posture changes, the researchers then addressed the link between these prodromal symptoms and the Mediterranean diet score for each of the 1731 individuals who did not have a Parkinson’s diagnosis.

Higher Mediterranean diet scores were associated with a lower probability of prodromal Parkinson’s. By splitting the whole sample into four groups, and comparing the groups with the lowest and highest Mediterranean diet scores, the researchers found that the high scorers were at a 21% lower risk for these early symptoms.

This was a population based, self-report study carried out in Greece in a relatively large group of people who volunteered to record their data. It is not clear whether this correlation indicates causation: that is, it is not clear whether this dietary factor lowers these prodromal symptoms, or whether people who experience less of this symptom burden are more likely to maintain a healthier diet, which may be Mediterranean. Prospective studies with appropriate controls could help clarify this important open question.

Alcalay, R. N., Gu, Y., Mejia-Santana, H., Cote, L., Marder, K. S., & Scarmeas, N. (2012). The association between Mediterranean diet adherence and Parkinson’s disease. Mov Disord, 27(6), 771-774: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3349773/

Gao, X., Chen, H., Fung, T. T., Logroscino, G., Schwarzschild, M. A., Hu, F. B., & Ascherio, A. (2007). Prospective study of dietary pattern and risk of Parkinson disease. Am J Clin Nutr, 86(5), 1486-1494: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2225168/

https://onlinelibrary.wiley.com/doi/abs/10.1002/mds.27489